This invention relates to couplings used for transmitting rotation from one shaft to another, and more particularly, to a coupling using an elastomeric belt with a retaining sleeve used to keep the belt in place.
Various types of flexible couplings have been used for connecting one shaft to another. These couplings compensate for relatively minor degrees of shaft misalignment which are normally encountered in manufacturing operations.
One type of prior art coupling uses two hubs, each hub having a plurality of projecting teeth extending from the hub face toward the other hub face. Such couplings, called jaw-type couplings, are sold by Lovejoy, Inc. of Downers Grove, Ill. The hubs are each mounted on one of the shafts. The teeth extending from each hub face are of a length so that they will be slightly separated from the other hub face when the coupling is assembled. The teeth, which are parallel to but overlap each other, are separated by spaces. An elastomeric element, often called a spider, occupies the plurality of spaces formed between adjacent teeth. Thus, the force from the teeth of the one hub is transmitted through the elastomeric element to the teeth of the other hub. These couplings operate with the elastomeric element in compression and have the characteristics of compactness, capable of transmitting large forces and continuing to transmit rotational forces even when the elastomeric element fails. This last characteristic can be an advantage or a shortcoming in that if the elastomeric element fails, the teeth of one hub strike the teeth of the other hub and continue to drive the driven shaft and any equipment to which it is connected. Thus, in an overload condition, the driven equipment is not protected by the coupling.
Another type of flexible coupling is illustrated in U.S. Pat. No. 5,139,460 by Hoyt, III et al. This coupling is similar to the above described coupling in that a pair of hubs each having extending teeth are mounted on their respective shafts. However, the teeth on one hub are parallel to and aligned with the teeth on the other hub. A belt surrounds the hubs and fills in the spaces between adjacent pairs of teeth. Projections on the belt engage receptacles on the hub teeth to prevent the hubs from moving apart. In this design, the belt operates in shear.
Advantages of this type of design are that the belt provides for misalignment between the shafts; the belt transmits power uniformly; the belt provides damping; and if the belt fails, the driven equipment is protected as it will essentially be disconnected from the drive shaft. Furthermore, this type of design allows the belt to be replaced without disassembling the hubs or moving the equipment connected to the shafts.
Another type of shear coupling is illustrated in U.S. Pat. No. 5,295,911 to Hoyt, III et al. This design illustrates teeth overlapping each other while using an elastomeric belt between overlapping teeth to transmit the torque. There is also shown a retainer ring surrounding the belt to keep the belt in place.
A problem arises in this coupling in that the retainer ring has a tendency to slip from its desired position of being centered on the belt. If the retainer ring slips off the belt, the belt will come loose and the coupling will disengage. One attempt at solving this problem has been to cut a groove or channel in the belt perpendicular to the edge of the belt. Another groove which is cut perpendicular to and intersects with the first groove extends a short distance around the circumference of the belt. There is a pin on the inside surface of the band which is received in the grooves. This design did not provide a completely satisfactory solution as the pin locked the band in place only when rotating in one direction. Thus, there has been, and is still the need, to provide a retainer band that will be securely retained on the belt regardless of the direction of rotation of the hubs.
Accordingly, it is an object of the invention to provide a flexible coupling which operates in shear and utilizes a retainer ring about the elastomeric belt.
It is a related object to provide a shear type flexible coupling which has a retainer ring securely, yet releasably fastened to the elastomeric belt. Yet another object is to provide such an elastomeric belt and retainer ring which secures the retainer ring to the belt regardless of the direction of rotation of the hubs.
The invention disclosed herein provides a shear-type flexible coupling in which the teeth on the hubs are in parallel alignment and spaced from each other. A flexible elastomeric belt fills the gaps between adjacent pairs of teeth. A retainer band is mounted around the belt to keep the belt securely in place. In a first embodiment, the exterior of the belt surface has a J-shaped groove cut therein, with one end extending to the edge of the belt. A locating pin on the inside of the retainer band is slid along the groove until the pin reaches the end of the groove at which point the retainer band is properly centered around the flexible belt.
In a second embodiment, the exterior of the belt surface has a groove cut axially on the outer surface of the belt from one edge of the belt to the other edge. Two perpendicular grooves extend in opposite directions from the axial groove. The locating pin on the retainer band can be slid along either of the perpendicular grooves to lock the retainer band in place regardless of the side from which the band is slid onto the belt or the direction of rotation of the coupling.